The NIS Domain

An NIS domain is a collection of machines which
share a common set of NIS maps. Each domain has a domain name and each machine
sharing the common set of maps belongs to that domain.

Any machine can belong to a given domain, as long as there is a server
for that domain's maps in the same network. An NIS client machine obtains
its domain name and binds to an NIS server as part of its boot process.